pg_stat_statements

1) see re: increasing shmmax http://stackoverflow.com/a/10629164/1283020

2) add to postgresql.conf:
shared_preload_libraries = 'pg_stat_statements'   # (change requires restart)
136 pg_stat_statements.max = 1000
137 pg_stat_statements.track = all

3) restart postgres

4) check it out in psql
psql: CREATE EXTENSION pg_stat_statements;
psql: \x
psql: SELECT query, calls, total_time, rows, 100.0 * shared_blks_hit /                                                                                                                                            nullif(shared_blks_hit + shared_blks_read, 0) AS hit_percent                                                                                                                 FROM pg_stat_statements ORDER BY total_time DESC LIMIT 5;